As the worldwide proliferation of the use of explosives within terrorist activities intensifies, governments from all over the world have hurried to establish security programs that can detect the presence of explosive materials, in an effort to protect their national security, citizenry and infrastructure. Such initiatives typically involve the use of search-and-detect explosives detecting canines (K9's), point-detection analytical instruments, or a combination of both, in the detection of explosives materials. To optimize these initiatives, there is need for the production of improved scent simulants to use as training aids within canine evaluation and training programs, and for the calibration of explosives detection instruments that detects through vapor sampling techniques.
Several scent simulants of explosive materials that can serve as training aids within canine detection programs have been developed. For example, U.S. Pat. Nos. 5,648,636, 5,413,812 and 5,359,936, granted to Simpson et al., relate to explosive scent simulants of detonable materials made through a combination of an already-fabricated explosive material with an inert material, either in a matrix or as a coating, where the explosive has a high surface ratio but small volume ratio.
In these embodiments, the explosive simulants may be fabricated by using either of two techniques. A first method involves the use of the standard slurry coatings to produce a material with a very high binder to explosive ratio without masking the explosive vapor, and a second method involves coating inert substrates with thin layers of the explosive. In both methods, actual explosives are used in the fabrication of the simulators—these explosives are diluted into slurries which are thereafter used to coat the surfaces of inert substrates.
Explosive simulants have also been fabricated for detection methods based on analytical principles other than that pertaining to vapor sampling. For example, U.S. Pat. No. 5,958,299 issued to Kury et al. relates to methods for fabricating non-energetic explosive simulants. The simulants imitate real explosives in terms of mass density, effective atomic number, x-ray transmission properties, and physical form. Since they are fabricated for a detection method based on analytical principles different from those pertaining to scent detection, they are not scent simulants and therefore not suitable for biological detection or for the calibration of instruments that rely on the principles of headspace vapor sampling to detect detonable materials.
US Patent 20060037509, issued to Phillip Kneisi, describes a scent training aid container for use in canine scent detection training. The container is made of a non-volatile material such as metals and ceramics and is of different dimensions. These training aids containers are designed to accommodate undiluted explosives in dimensions less than the explosive's critical thickness and serve as a scent source for scent training. The patent pertains only to the container and is required to be filled with actual explosives and explosive materials.
With all the advances made in the production of explosive scent simulants, there are still limitations that currently available and traditional slurry methods lend to the formation of optimized scent simulants for search-and-detect creature training and instrument calibration.
One limitation pertains to the loss of the more volatile components within the explosive material used in the production of the simulant, during the mechanical mixing processes employed in the formation of the simulant. During mechanical mixing, the heat of the mixing process results in a drastic reduction in, and, in some cases, the complete loss of, the more volatile components of the explosive material being used in the production of the simulant and the production of a scent simulant with an incomplete scent signature.
Another limitation occurs during attempts to evaporate the solvent used in a slurry making process, whereby all components within the explosive material being used in the production of the simulant, and that has a boiling point that is lower than that of the solvent used in the slurry making process, also evaporates from the slurry. The low boiling-point solvent might also lead to the low temperature evaporation of some components which, although having a higher boiling point, are miscible with the solvent.
Another limiting factor is the introduction of new odors. Since, in most cases, the solvent used in making the slurry coatings is different from any of the solvents used typically used during the manufacture of these explosives, drying of the slurry results in the entrapment of these solvents within the simulants formed, through inclusion within the structure of the simulant during crystallization, which concomitantly leads into the introduction of new odors within the headspace scent signature of the simulant which is not present within the explosive material being slurried or simulated.
Yet another limitation on presently available methods of making scent simulants is the sensitivity of certain explosives. There exist classes of explosives that need detection but for which scent simulants and training aids for search-and-detect creatures or instrument detection are unavailable simply because such explosives are so sensitive to storage, shock friction, static and temperature that they cannot be transported, handled, or stored in the bulk quantities needed for a commercialized production of scent simulants using prior art methods, nor can they be used within a formulation process that requires a direct handling and mixing of actual explosives into a slurry.
Particular amongst such explosives are detonable explosives such as nitroglycerin, and the group of explosives known as entropy-burst explosives, which, unlike typical detonable explosives, are extremely sensitive to shock, friction, and long term storage.
In view of the difficulties associated with the forming scent simulants and K9 detection training aids of very sensitive explosives using traditional slurry methods, there is a continuing need for new preparative methods for these simulants that is easy, convenient, safe, inexpensive, covers the whole spectrum of explosives needing detection, and still leads to the production of superior explosives detecting canine training aids and explosives detection analytical-instrument calibration aids.